/** 
 * @file llaccordionctrl.cpp
 * @brief Accordion panel  implementation
 *
 * $LicenseInfo:firstyear=2009&license=viewergpl$
 * 
 * Copyright (c) 2009, Linden Research, Inc.
 * 
 * Second Life Viewer Source Code
 * The source code in this file ("Source Code") is provided by Linden Lab
 * to you under the terms of the GNU General Public License, version 2.0
 * ("GPL"), unless you have obtained a separate licensing agreement
 * ("Other License"), formally executed by you and Linden Lab.  Terms of
 * the GPL can be found in doc/GPL-license.txt in this distribution, or
 * online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
 * 
 * There are special exceptions to the terms and conditions of the GPL as
 * it is applied to this Source Code. View the full text of the exception
 * in the file doc/FLOSS-exception.txt in this software distribution, or
 * online at
 * http://secondlifegrid.net/programs/open_source/licensing/flossexception
 * 
 * By copying, modifying or distributing this software, you acknowledge
 * that you have read and understood your obligations described above,
 * and agree to abide by those obligations.
 * 
 * ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
 * WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
 * COMPLETENESS OR PERFORMANCE.
 * $/LicenseInfo$
 */
#include "linden_common.h"

#include "llaccordionctrl.h"
#include "llaccordionctrltab.h"

#include "lluictrlfactory.h" // builds floaters from XML

#include "llwindow.h"
#include "llfocusmgr.h"
#include "lllocalcliprect.h"

#include "boost/bind.hpp"

static const S32 DRAGGER_BAR_MARGIN = 4;
static const S32 DRAGGER_BAR_HEIGHT = 5;
static const S32 BORDER_MARGIN = 2;
static const S32 PARENT_BORDER_MARGIN = 5;

static const S32 panel_delta = DRAGGER_BAR_MARGIN;  // Distanse between two panels 

static const S32 HORIZONTAL_MULTIPLE = 8;
static const S32 VERTICAL_MULTIPLE = 16;
static const F32 MIN_AUTO_SCROLL_RATE = 120.f;
static const F32 MAX_AUTO_SCROLL_RATE = 500.f;
static const F32 AUTO_SCROLL_RATE_ACCEL = 120.f;


// LLAccordionCtrl =================================================================|

static LLDefaultChildRegistry::Register<LLAccordionCtrl>	t2("accordion");


LLAccordionCtrl::LLAccordionCtrl(const Params& params):LLPanel(params)
 , mFitParent(params.fit_parent)
 , mAutoScrolling( false )
 , mAutoScrollRate( 0.f )
{
  mSingleExpansion = params.single_expansion;
	if(mFitParent && !mSingleExpansion)
	{
		llinfos << "fit_parent works best when combined with single_expansion" << llendl;
	}
}

LLAccordionCtrl::LLAccordionCtrl() : LLPanel()
 , mAutoScrolling( false )
 , mAutoScrollRate( 0.f )
{
	mSingleExpansion = false;
	mFitParent = false;
	LLUICtrlFactory::getInstance()->buildPanel(this, "accordion_parent.xml");	
}

//---------------------------------------------------------------------------------
void LLAccordionCtrl::draw()
{
	if (mAutoScrolling)
	{
		// add acceleration to autoscroll
		mAutoScrollRate = llmin(mAutoScrollRate + (LLFrameTimer::getFrameDeltaTimeF32() * AUTO_SCROLL_RATE_ACCEL), MAX_AUTO_SCROLL_RATE);
	}
	else
	{
		// reset to minimum for next time
		mAutoScrollRate = MIN_AUTO_SCROLL_RATE;
	}
	// clear this flag to be set on next call to autoScroll
	mAutoScrolling = false;

	LLRect local_rect(0, getRect().getHeight(), getRect().getWidth(), 0);
	
	LLLocalClipRect clip(local_rect);
	
	LLPanel::draw();
	/*
	S32 width = getRect().getWidth();
	S32 height = getRect().getHeight();

	gl_rect_2d(0, 0 , width - 1 ,height - 1,LLColor4::green,true);
	gl_line_2d(0, 0 , width - 1 ,height - 1,LLColor4::black);
	*/
}


//---------------------------------------------------------------------------------
BOOL LLAccordionCtrl::postBuild()
{
	static LLUICachedControl<S32> scrollbar_size ("UIScrollbarSize", 0);

	LLRect scroll_rect;
	scroll_rect.setOriginAndSize( 
		getRect().getWidth() - scrollbar_size,
		1,
		scrollbar_size,
		getRect().getHeight() - 1);
	

	LLScrollbar::Params sbparams;
	sbparams.name("scrollable vertical");
	sbparams.rect(scroll_rect);
	sbparams.orientation(LLScrollbar::VERTICAL);
	sbparams.doc_size(mInnerRect.getHeight());
	sbparams.doc_pos(0);
	sbparams.page_size(mInnerRect.getHeight());
	sbparams.step_size(VERTICAL_MULTIPLE);
	sbparams.follows.flags(FOLLOWS_RIGHT | FOLLOWS_TOP | FOLLOWS_BOTTOM);
	sbparams.change_callback(boost::bind(&LLAccordionCtrl::onScrollPosChangeCallback, this, _1, _2));
	
	mScrollbar = LLUICtrlFactory::create<LLScrollbar> (sbparams);
	LLView::addChild( mScrollbar );
	mScrollbar->setVisible( false );
	mScrollbar->setFollowsRight();
	mScrollbar->setFollowsTop();
	mScrollbar->setFollowsBottom();

	//if it was created from xml...
	std::vector<LLUICtrl*> accordion_tabs;
	for(child_list_const_iter_t it = getChildList()->begin(); 
		getChildList()->end() != it; ++it)
	{
		LLAccordionCtrlTab* accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(*it);
		if(accordion_tab == NULL)
			continue;
		if(std::find(mAccordionTabs.begin(),mAccordionTabs.end(),accordion_tab) == mAccordionTabs.end())
		{
			accordion_tabs.push_back(accordion_tab);
		}
	}

	for(std::vector<LLUICtrl*>::reverse_iterator it = accordion_tabs.rbegin();it!=accordion_tabs.rend();++it)
		addCollapsibleCtrl(*it);

	arrange	();

	if(mSingleExpansion)
	{
		if(!mAccordionTabs[0]->getDisplayChildren())
			mAccordionTabs[0]->setDisplayChildren(true);
		for(size_t i=1;i<mAccordionTabs.size();++i)
		{
			if(mAccordionTabs[i]->getDisplayChildren())
				mAccordionTabs[i]->setDisplayChildren(false);
		}
	}

	return TRUE;
}


//---------------------------------------------------------------------------------
LLAccordionCtrl::~LLAccordionCtrl()
{
  mAccordionTabs.clear();
}

//---------------------------------------------------------------------------------

void LLAccordionCtrl::reshape(S32 width, S32 height, BOOL called_from_parent)
{
	// adjust our rectangle
	LLRect rcLocal = getRect();
	rcLocal.mRight = rcLocal.mLeft + width;
	rcLocal.mTop = rcLocal.mBottom + height;

	setRect(rcLocal);

	arrange();
}

//---------------------------------------------------------------------------------
BOOL LLAccordionCtrl::handleRightMouseDown(S32 x, S32 y, MASK mask)
{
	return LLPanel::handleRightMouseDown(x, y, mask);
}

//---------------------------------------------------------------------------------
void LLAccordionCtrl::shiftAccordionTabs(S16 panel_num, S32 delta)
{
	for(size_t i = panel_num; i < mAccordionTabs.size(); i++ )
	{
		ctrlShiftVertical(mAccordionTabs[i],delta);
	}	
}


//---------------------------------------------------------------------------------
void LLAccordionCtrl::onCollapseCtrlCloseOpen(S16 panel_num) 
{
	if(mSingleExpansion)
	{
		for(size_t i=0;i<mAccordionTabs.size();++i)
		{
			if(i==panel_num)
				continue;
			if(mAccordionTabs[i]->getDisplayChildren())
				mAccordionTabs[i]->setDisplayChildren(false);
		}

	}
	arrange();
}

void LLAccordionCtrl::show_hide_scrollbar(S32 width, S32 height)
{
	calcRecuiredHeight();
	if(getRecuiredHeight() > height )
		showScrollbar(width,height);
	else
		hideScrollbar(width,height);
}

void	LLAccordionCtrl::showScrollbar(S32 width, S32 height)
{
	bool was_visible = mScrollbar->getVisible();

	mScrollbar->setVisible(true);
	
	static LLUICachedControl<S32> scrollbar_size ("UIScrollbarSize", 0);

	ctrlSetLeftTopAndSize(mScrollbar
		,width-scrollbar_size - PARENT_BORDER_MARGIN/2
		,height-PARENT_BORDER_MARGIN
		,scrollbar_size
		,height-2*PARENT_BORDER_MARGIN);
	
	mScrollbar->setPageSize(height);
	mScrollbar->setDocParams(mInnerRect.getHeight(),mScrollbar->getDocPos());

	if(was_visible)
	{
		S32 scroll_pos = llmin(mScrollbar->getDocPos(), getRecuiredHeight() - height - 1);
		mScrollbar->setDocPos(scroll_pos);
	}
}

void	LLAccordionCtrl::hideScrollbar( S32 width, S32 height )
{
	if(mScrollbar->getVisible() == false)
		return;
	mScrollbar->setVisible(false);

	static LLUICachedControl<S32> scrollbar_size ("UIScrollbarSize", 0);

	S32 panel_width = width - 2*BORDER_MARGIN;

	//reshape all accordeons and shift all draggers
	for(size_t i=0;i<mAccordionTabs.size();++i)
	{
		LLRect panel_rect = mAccordionTabs[i]->getRect();
		ctrlSetLeftTopAndSize(mAccordionTabs[i],panel_rect.mLeft,panel_rect.mTop,panel_width,panel_rect.getHeight());
	}

	mScrollbar->setDocPos(0);

	if(mAccordionTabs.size()>0)
	{
		S32 panel_top = height - BORDER_MARGIN;		  // Top coordinate of the first panel
		S32 diff = panel_top - mAccordionTabs[0]->getRect().mTop;
		shiftAccordionTabs(0,diff);
	}
}


//---------------------------------------------------------------------------------
S32 LLAccordionCtrl::calcRecuiredHeight()
{
	S32 rec_height = 0;
	
	std::vector<LLAccordionCtrlTab*>::iterator panel;
	for(panel=mAccordionTabs.begin(); panel!=mAccordionTabs.end(); ++panel)
	{
		LLAccordionCtrlTab* accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(*panel);
		if(accordion_tab && accordion_tab->getVisible())
		{
			rec_height += accordion_tab->getRect().getHeight();
		}
	}

	mInnerRect.setLeftTopAndSize(0,rec_height + BORDER_MARGIN*2,getRect().getWidth(),rec_height + BORDER_MARGIN);

	return mInnerRect.getHeight();
}

//---------------------------------------------------------------------------------
void LLAccordionCtrl::ctrlSetLeftTopAndSize(LLView* panel, S32 left, S32 top, S32 width, S32 height)
{
	if(!panel)
		return;
	LLRect panel_rect = panel->getRect();
	panel_rect.setLeftTopAndSize( left, top, width, height);
	panel->reshape( width, height, 1);
	panel->setRect(panel_rect);
}

void LLAccordionCtrl::ctrlShiftVertical(LLView* panel,S32 delta)
{
	if(!panel)
		return;
	panel->translate(0,delta);
}

//---------------------------------------------------------------------------------

void LLAccordionCtrl::addCollapsibleCtrl(LLView* view)
{
	LLAccordionCtrlTab* accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(view);
	if(!accordion_tab)
		return;
	if(std::find(getChildList()->begin(),getChildList()->end(),accordion_tab) == getChildList()->end())
		addChild(accordion_tab);
	mAccordionTabs.push_back(accordion_tab);
	
	accordion_tab->setDropDownStateChangedCallback( boost::bind(&LLAccordionCtrl::onCollapseCtrlCloseOpen, this, mAccordionTabs.size() - 1) );

}

void	LLAccordionCtrl::arrangeSinge()
{
	S32 panel_left = BORDER_MARGIN;	  // Margin from left side of Splitter
	S32 panel_top = getRect().getHeight() - BORDER_MARGIN;		  // Top coordinate of the first panel
	S32 panel_width = getRect().getWidth() - 4;		  // Top coordinate of the first panel
	S32 panel_height;

	S32 collapsed_height = 0;

	for(size_t i=0;i<mAccordionTabs.size();++i)
	{
		LLAccordionCtrlTab* accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[i]);
		
		if(accordion_tab->getVisible() == false) //skip hidden accordion tabs
			continue;
		if(!accordion_tab->isExpanded() )
		{
			collapsed_height+=mAccordionTabs[i]->getRect().getHeight();
		}
	}

	S32 expanded_height = getRect().getHeight() - BORDER_MARGIN - collapsed_height;
	
	for(size_t i=0;i<mAccordionTabs.size();++i)
	{
		LLAccordionCtrlTab* accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[i]);
		
		if(accordion_tab->getVisible() == false) //skip hidden accordion tabs
			continue;
		if(!accordion_tab->isExpanded() )
		{
			panel_height = accordion_tab->getRect().getHeight();
		}
		else
		{
			panel_height = expanded_height;
		}
		ctrlSetLeftTopAndSize(mAccordionTabs[i], panel_left, panel_top, panel_width, panel_height);
		panel_top-=mAccordionTabs[i]->getRect().getHeight();
	}
}

void	LLAccordionCtrl::arrangeMultiple()
{
	S32 panel_left = BORDER_MARGIN;	  // Margin from left side of Splitter
	S32 panel_top = getRect().getHeight() - BORDER_MARGIN;		  // Top coordinate of the first panel
	S32 panel_width = getRect().getWidth() - 4;		  // Top coordinate of the first panel

	//Calculate params	
	for(size_t i = 0; i < mAccordionTabs.size(); i++ )
	{
		LLAccordionCtrlTab* accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[i]);
		
		if(accordion_tab->getVisible() == false) //skip hidden accordion tabs
			continue;
		
		if(!accordion_tab->isExpanded() )
		{
			ctrlSetLeftTopAndSize(mAccordionTabs[i], panel_left, panel_top, panel_width, accordion_tab->getRect().getHeight());
			panel_top-=mAccordionTabs[i]->getRect().getHeight();
		}
		else
		{
			S32 panel_height = accordion_tab->getRect().getHeight();
			
			if(mFitParent)
			{
				// all expanded tabs will have equal height
				panel_height = calcExpandedTabHeight(i, panel_top);
				ctrlSetLeftTopAndSize(accordion_tab, panel_left, panel_top, panel_width, panel_height);

				// try to make accordion tab fit accordion view height.
				// Accordion View should implement getRequiredRect() and provide valid height
				S32 optimal_height = accordion_tab->getAccordionView()->getRequiredRect().getHeight();
				optimal_height += accordion_tab->getHeaderHeight() + 2 * BORDER_MARGIN;
				if(optimal_height < panel_height)
				{
					panel_height = optimal_height;
				}

				// minimum tab height is equal to header height
				if(mAccordionTabs[i]->getHeaderHeight() > panel_height)
				{
					panel_height = mAccordionTabs[i]->getHeaderHeight();
				}
			}
			
			ctrlSetLeftTopAndSize(mAccordionTabs[i], panel_left, panel_top, panel_width, panel_height);
			panel_top-=panel_height;
			
		}
	}	

	show_hide_scrollbar(getRect().getWidth(),getRect().getHeight());

	updateLayout(getRect().getWidth(),getRect().getHeight());
}


void LLAccordionCtrl::arrange()
{
	if( mAccordionTabs.size() == 0)
	{
		//We do not arrange if we do not have what should be arranged
		return;
	}


	if(mAccordionTabs.size() == 1)
	{
		S32 panel_top = getRect().getHeight() - BORDER_MARGIN;		  // Top coordinate of the first panel
		S32 panel_width = getRect().getWidth() - 4;		  // Top coordinate of the first panel
		
		LLAccordionCtrlTab* accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[0]);
		
		LLRect panel_rect = accordion_tab->getRect();
		
		S32 panel_height = getRect().getHeight() - 2*BORDER_MARGIN;

		ctrlSetLeftTopAndSize(accordion_tab,panel_rect.mLeft,panel_top,panel_width,panel_height);
		
		show_hide_scrollbar(getRect().getWidth(),getRect().getHeight());
		return;

	}

	if(mSingleExpansion)
		arrangeSinge ();
	else
		arrangeMultiple ();
}

//---------------------------------------------------------------------------------

BOOL LLAccordionCtrl::handleScrollWheel		( S32 x, S32 y, S32 clicks )
{
	if(LLPanel::handleScrollWheel(x,y,clicks))
		return TRUE;
	if( mScrollbar->getVisible() && mScrollbar->handleScrollWheel( 0, 0, clicks ) )
		return TRUE;
	return false;

}

BOOL LLAccordionCtrl::handleKeyHere			(KEY key, MASK mask)
{
	if( mScrollbar->getVisible() && mScrollbar->handleKeyHere( key,mask ) )
		return TRUE;
	return LLPanel::handleKeyHere(key,mask);
}

BOOL LLAccordionCtrl::handleDragAndDrop		(S32 x, S32 y, MASK mask,
											 BOOL drop,
											 EDragAndDropType cargo_type,
											 void* cargo_data,
											 EAcceptance* accept,
											 std::string& tooltip_msg)
{
	// Scroll folder view if needed.  Never accepts a drag or drop.
	*accept = ACCEPT_NO;
	BOOL handled = autoScroll(x, y);

	if( !handled )
	{
		handled = childrenHandleDragAndDrop(x, y, mask, drop, cargo_type,
											cargo_data, accept, tooltip_msg) != NULL;
	}
	return TRUE;
}

BOOL LLAccordionCtrl::autoScroll		(S32 x, S32 y)
{
	static LLUICachedControl<S32> scrollbar_size ("UIScrollbarSize", 0);

	bool scrolling = false;
	if( mScrollbar->getVisible() )
	{
		LLRect rect_local( 0, getRect().getHeight(), getRect().getWidth() - scrollbar_size, 0 );
		LLRect screen_local_extents;

		// clip rect against root view
		screenRectToLocal(getRootView()->getLocalRect(), &screen_local_extents);
		rect_local.intersectWith(screen_local_extents);

		// autoscroll region should take up no more than one third of visible scroller area
		S32 auto_scroll_region_height = llmin(rect_local.getHeight() / 3, 10);
		S32 auto_scroll_speed = llround(mAutoScrollRate * LLFrameTimer::getFrameDeltaTimeF32());

		LLRect bottom_scroll_rect = screen_local_extents;
		bottom_scroll_rect.mTop = rect_local.mBottom + auto_scroll_region_height;
		if( bottom_scroll_rect.pointInRect( x, y ) && (mScrollbar->getDocPos() < mScrollbar->getDocPosMax()) )
		{
			mScrollbar->setDocPos( mScrollbar->getDocPos() + auto_scroll_speed );
			mAutoScrolling = true;
			scrolling = true;
		}

		LLRect top_scroll_rect = screen_local_extents;
		top_scroll_rect.mBottom = rect_local.mTop - auto_scroll_region_height;
		if( top_scroll_rect.pointInRect( x, y ) && (mScrollbar->getDocPos() > 0) )
		{
			mScrollbar->setDocPos( mScrollbar->getDocPos() - auto_scroll_speed );
			mAutoScrolling = true;
			scrolling = true;
		}
	}
	return scrolling;
}

void	LLAccordionCtrl::updateLayout	(S32 width, S32 height)
{
	S32 panel_top = height - BORDER_MARGIN ;
	if(mScrollbar->getVisible())
		panel_top+=mScrollbar->getDocPos();

	S32 panel_width = width - 2*BORDER_MARGIN;

	static LLUICachedControl<S32> scrollbar_size ("UIScrollbarSize", 0);
	if(mScrollbar->getVisible())
		panel_width-=scrollbar_size;

	//set sizes for first panels and dragbars
	for(size_t i=0;i<mAccordionTabs.size();++i)
	{
		if(!mAccordionTabs[i]->getVisible())
			continue;
		LLRect panel_rect = mAccordionTabs[i]->getRect();
		ctrlSetLeftTopAndSize(mAccordionTabs[i],panel_rect.mLeft,panel_top,panel_width,panel_rect.getHeight());
		panel_top-=panel_rect.getHeight();
	}
}

void	LLAccordionCtrl::onScrollPosChangeCallback(S32, LLScrollbar*)
{
	updateLayout(getRect().getWidth(),getRect().getHeight());
}
void	LLAccordionCtrl::onOpen		(const LLSD& key)
{
	for(size_t i=0;i<mAccordionTabs.size();++i)
	{
		LLAccordionCtrlTab* accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[i]);
		LLPanel* panel = dynamic_cast<LLPanel*>(accordion_tab->getAccordionView());
		if(panel!=NULL)
		{
			panel->onOpen(key);
		}
	}
}
S32	LLAccordionCtrl::notifyParent(const LLSD& info)
{
	if(info.has("action"))
	{
		std::string str_action = info["action"];
		if(str_action == "size_changes")
		{
			//
			arrange();
			return 1;
		}
		else if(str_action == "select_next")
		{
			for(size_t i=0;i<mAccordionTabs.size();++i)
			{
				LLAccordionCtrlTab* accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[i]);
				if(accordion_tab->hasFocus())
				{
					while(++i<mAccordionTabs.size())
					{
						if(mAccordionTabs[i]->getVisible())
							break;
					}
					if(i<mAccordionTabs.size())
					{
						accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[i]);
						accordion_tab->notify(LLSD().with("action","select_first"));
						return 1;
					}
					break;
				}
			}
			return 0;
		}
		else if(str_action == "select_prev")
		{
			for(size_t i=0;i<mAccordionTabs.size();++i)
			{
				LLAccordionCtrlTab* accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[i]);
				if(accordion_tab->hasFocus() && i>0)
				{
					while(i>0)
					{
						if(mAccordionTabs[--i]->getVisible())
							break;
					}
					
					accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[i]);
					accordion_tab->notify(LLSD().with("action","select_last"));
					return 1;
				}
			}
			return 0;
		}
	}
	else if (info.has("scrollToShowRect"))
	{
		LLRect screen_rc, local_rc;
		screen_rc.setValue(info["scrollToShowRect"]);
		screenRectToLocal(screen_rc, &local_rc);

		// Translate to parent coordinatess to check if we are in visible rectangle
		local_rc.translate( getRect().mLeft, getRect().mBottom );

		if ( !getRect().contains (local_rc) )
		{
			// Back to local coords and calculate position for scroller
			S32 bottom = mScrollbar->getDocPos() - local_rc.mBottom + getRect().mBottom;
			S32 top = mScrollbar->getDocPos() - local_rc.mTop + getRect().mTop;

			S32 scroll_pos = llclamp(mScrollbar->getDocPos(),
									 bottom, // min vertical scroll
									 top); // max vertical scroll 

			mScrollbar->setDocPos( scroll_pos );
		}
		return 1;
	}
	return LLPanel::notifyParent(info);
}
void	LLAccordionCtrl::reset		()
{
	if(mScrollbar)
		mScrollbar->setDocPos(0);
}

S32 LLAccordionCtrl::calcExpandedTabHeight(S32 tab_index /* = 0 */, S32 available_height /* = 0 */)
{
	if(tab_index < 0)
	{
		return available_height;
	}

	S32 collapsed_tabs_height = 0;
	S32 num_expanded = 0;

	for(size_t n = tab_index; n < mAccordionTabs.size(); ++n)
	{
		if(!mAccordionTabs[n]->isExpanded())
		{
			collapsed_tabs_height += mAccordionTabs[n]->getHeaderHeight();
		}
		else
		{
			++num_expanded;
		}
	}

	if(0 == num_expanded)
	{
		return available_height;
	}

	S32 expanded_tab_height = available_height - collapsed_tabs_height - BORDER_MARGIN; // top BORDER_MARGIN is added in arrange(), here we add bottom BORDER_MARGIN
	expanded_tab_height /= num_expanded;
	return expanded_tab_height;
}